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Journal of Advanced Dielectrics 2023年第6期13卷 45-48页

作者： A.Pelaiz-Barranco Y.Perez-Martín o.garcía-zaldívar Y.Gagou Grupo de Materiales Ferroicos Facultad de Física-IMRE Universidad de la Habana.San Lazaroy LVedado.La Habana 10400Cuba LPMC Universite de Picardie Jules Verne 33 rue Saint-Leu80039 Amiens CedexFrance

(Pb_(0.8)Ba_(0.2))[(Zn_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)]o_(3)relaxor-type ferroelectric ceramics was obtained via classical solid-state *** hysteresis loop results were discussed in the frame of ergodicity criterium around the characteristic ferroelectric relaxor freezing *** hysteresis loops were observed below the freezing temperature reflecting an ergodic relaxor *** this temperature,estimated around 223K for the studied system,larger and unsaturated like ferroelectric hysteresis loops were *** temperature also coincides with the slope change on maximum polarization and inflection point of remnant polarization *** storage,energy loss and efficiency values were determined in a wide temperature *** the recoverable energy density shows relatively low values(0.23 J/cm^(3)),there are interesting behaviors for this parameter and for the efficiency,since the two physical quantities increase versus temperature and the efficiency even reaches the value of 97%.

关键词： Relaxors ferroelectrics energy storage freezing temperature

Equivalent circuit for the characterization of the resonance mode in piezoelectric systems

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Journal of Advanced Dielectrics 2015年第4期5卷 37-41页

作者： Y.Fernández-Afonso o.garcía-zaldívar F.Calderón-Piñar Centrode Estudios Avanzadosde Cuba Kilómetro 1y 1/2 Carreter a San Antonio de los Baños Valle Grande La LisaHabanaCuba Facultadde Física-Instituto de Cienciay Tecnología de Materiales Universidad de La Habana.San LázaroyL Vedado.La Habana 10400 Cuba CINVESTAV-Unidad Querétaro Libramiento Norponiente No.2000 Realde Juriquilla QuerétaroQro.76230México

The impedance properties in polarized piezoelectric can be described by electric equivalent *** classic circuit used in the literature to describe real systems is formed by one resistor(R),one inductance(L)and one capacitance C connected in series and one capacity(C_(0))connected in parallel with the ***,the equation that describe the resonance and anti-resonance frequencies depends on a complex manner of R,L,C and C_(0).In this work is proposed a simpler model formed by one inductance(L)and one capacity(C)in series;one capacity(C_(0))in parallel;one resistor(R_(p))in parallel and one resistor(Rs)in series with other *** the traditional circuit,the equivalent circuit elements in the proposed model can be simply determined by knowing the experimental values of the resonance frequency fr,anti-resonance frequency fa,impedance module at resonance frequency|Z|,impedance module at anti-resonance frequency|Za|and low frequency capacitance C_(0),without ftting the im-pedance experimental data to the obtained equation.

关键词： Piezoelectric equivalent circuit electromechanic

Relaxor ferroelectric behavior:An approach considering both the dipolar and electrical conductivity contributions

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Journal of Advanced Dielectrics 2021年第3期11卷 51-55页

作者： C.Carreras-Casas o.garcía-zaldívar A.Peláiz-Barranco Y.González-Abreu F.Calderón-Pinar J.D.S.Guerra Grupo de Materiales Ferroicos Facultad de Física-Instituto de Ciencia y Tecnología de Materiales Universidad de La Habana La Habana 10400Cuba Grupo de Ferroelétricos e Materiais Multifuncionais Instituto de Física Universidade Federal de Uberlandia UberlandiaMinas Gerais38408-100Brazil

The relaxor behavior of PLZT ferroelectric ceramics has been analyzed in a wide frequency and temperature ranges,below and above the temperature for the formation of the so-called polar nano-regions(PNRs).An approximation to the dynamical behavior of the PNRs has been discussed using Cole-Cole’s relaxation model and Jonscher’s Universal Relaxation *** analysis considers both the dipolar contribution and those ones associated with DC and AC electric conductivities,this latter not being previously reported in the literature for relaxor *** effectiveness of the developed model has been verified from the agreement between the experimental data and the theoretical *** study also offers an indirect method to predict the DC component of the electrical conductivity.

关键词： Relaxor ferroelectrics dielectric response modeling conductivity Cole-Cole

Hepatic rupture secondary to HELLP syndrome: outcomes in three cases

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World Journal of Emergency Medicine 2024年第1期15卷 56-58页

作者： Salvador Gomez-Carro Ruben R.Lozano-Salazar Kassandra Santos-zaldívar Victor Andres Villasuso-Alcocer Nina Méndez-Domínguez o'Horan General Hospital Merida 97000Mexico Highly Specialized Hospital of the Yucatan Peninsula Merida 97134Mexico National Institute of Perinatology.Mexico City 11000 Mexico

Hypertensive disorders of pregnancy,including chronic hypertension,gestational hypertension,and preeclampsia,are the most common complications in pregnant women,affecting approximately 15%of pregnancies.[1,2]Hemolysis,elevated liver enzymes,and low platelet count(HELLP syndrome)can occur in 0.2%-0.6%of all pregnancies,and 10%-15%of patients are diagnosed with preeclampsia.[3,4]Among its severe complications,liver hematoma is remarkable and may lead to liver *** identification of HELLP syndrome is crucial for proper therapeutic management and to avoid fatal outcomes[4,5]since when a hepatic hematoma occurs,the risk of rupture increases to 12%.[3,5]

关键词： rupture HELLP hypertension pregnancy

BiFeo_(3) codoping with Ba,La and Ti:Magnetic and structural studies

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Journal of Advanced Dielectrics 2015年第4期5卷 53-60页

作者： o.garcía-zaldívar S.Díaz-Castañón F.J.Espinoza-Beltran M.A.Hernández-Landaverde G.López J.Faloh-Gandarilla F.Calderón-Piñar Facultad de Física-Instituto de Ciencia y Tecnología de Materiales Universidad de La Habana San Láazaro y L VedadoLa Habana 10400Cuba CINVESTAV-Unidad Querétaro Libramiento Norponiente No.2000 Real de JuriquillaQuerétaroQro.76230México Instituto Latino-Americanode Ciênciasda Vidaeda Natureza Universidade Federalda Integração Latino-Americana (ILCVN-UNILA)Avenida Tancredo NevesPTIBloco 6 CEP:85866-000-Foz do Iguaçu-ParanaBrazil División Materiales Avanzados Instituto Potosinode Investigación Científica Tecnológica San Luis Potosí CP78216Méexico

Conventional solid state reaction method,from oxides and carbonates,was employed to prepare bismuth(Bi)-based multiferroic *** undoped BiFeo_(3)(BFo)and the codoped system with Ba,La and Ti(Bi_(1-x)Ba_(x)Fe_(1-y)Ti_(y)o_(3),Bi_(1-x-z)Ba_(x)LazFe_(1-y)Tiyo_(3))with x,y,z=0.1 were prepared stoichiometrically and sintered at two different *** structural and magnetic properties were investigated at room *** measurements confirm the obtaining of the rhombohedral perovskite structure of the BFo family *** the undoped system,some reflections of undesired phases are present for two different sintering temperatures,while for the doped system only one phase is present for both *** magnetic characterization at room temperature revealed remarkable differences between the ceramic *** results show that for undoped BFo system,spontaneous magnetization is not observed at room ***,in doped one,a well-defined ferromagnetic behavior is observed at room temperature,possible,due to the suppression of the spatially modulated spin structure of BFo promoted by the reduction of the rhombohedral distortion and the weakening of the Bi-o *** XPS results confirm the presence of oxygen vacancies and the coexistence of Fe^(3+)and Fe^(2+) in all the studied *** measurements reveal that the dopant incorporation has not a direct effect in Neel temperature but possibly yes in ferroelectric-paraelectric transition.

关键词： Multiferroics XPS magnetic bismuth ferrite BiFeo_(3)

on the analytical solution of transient friction in channel flows

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Applied Mathematics and Mechanics(English Edition) 2024年第8期45卷 1447-1466页

作者： F.J.garcíA-garcíA P.FARI?AS-ALvarI?o Department of Naval & Industrial Engineering Polytechnic School of EngineeringUniversity of A Coru?a Campus Industrial de Ferrol Integraciones Técnicas de Seguridad S.A. Pol.Ind.Espíritu Santo

The transient friction in channel mean flows is the sum of two contributions,i.e., the underlying laminar flow(ULF) and the purely turbulent component(PTC), and the contributions are analyzed separately by theoretical experiments. It is found that,the transient friction may be higher or remarkably lower than that in equal-Reynolds number steady-state flows. The universal time constant for plane-parallel laminar flows is reported, and the role of the time constant in a turbulent mean flow is examined. It is shown that the time constant is related to the turbulence's frozen time. Finally, a study of the logarithmic layer during the transient flow is accomplished, which shows that the logarithmic layer is destroyed.

关键词： 76D05 76D06 76F55 o361 transient flow transient friction unsteady channel flow

Myelin histology:a key tool in nervous system research

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Neural Regeneration Research 2024年第2期19卷 277-281页

作者： Óscar Darío.garcía-garcía Víctor Carriel Jesús Chato-Astrain Department of Histology Tissue Engineering GroupUniversity of Granada&Instituto de Investigación Biosanitaria ibs.GRANADAGranadaSpain

The myelin sheath is a lipoprotein-rich,multilayered structure capable of increasing conduction velocity in central and peripheral myelinated nerve *** to the complex structure and composition of myelin,various histological techniques have been developed over the centuries to evaluate myelin under normal,pathological or experimental ***,methods to assess myelin integrity or content are key tools in both clinical diagnosis and neuroscience *** this review,we provide an updated summary of the composition and structure of the myelin sheath and discuss some histological procedures,from tissue fixation and processing techniques to the most used and practical myelin histological staining *** the lipoprotein nature of myelin,the main features and technical details of the different available methods that can be used to evaluate the lipid or protein components of myelin are described,as well as the precise ultrastructural techniques.

关键词： fluorescence microscopy histology light microscopy lipid histochemistry metallographic techniques myelin histochemistry myelin immunohistochemistry myelin structure&composition myelin ultrastructural evaluation tissue fixation&processing

Quality assessment of the Topo-Iberia CGPS stations and data quality's effects on postfit ionosphere-free phase residuals

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Geodesy and Geodynamics 2024年第2期15卷 189-199页

作者： Juan A.garcía-Armenteros Center for Advanced Studies in Earth Sciences Energy and Environment(CEACTEMA)University of Jaén23071 JaenSpain

This paper analyzed GPS data from the Topo-Iberia network spanning almost 12 years(2008-2020).The data quality information for all 26 Topo-Iberia stations is provided for the first time,complementing the Spanish Geological Survey’s storage *** analyses based on quality indicators obtained using TEQC have been carried *** guidelines and data quality information from the IGS stations have been considered as the quality references,with the stations ALJI,EPCU,and TIoU standing out as the worst stations,while on the contrary,FUEN,PALM,PILA,and TRIA meet the quality requirements to become an IGS *** relationship between the GPS data quality and their GAMIT-and Gipsy X-derived postfit ionosphere-free phase residuals has also been investigated,and the results reveal an inversely proportional *** has been found that the stations showing an increase in elevation of the horizon line,also show an increase in cycle slips and multipath,are among the poorest quality stations,and among those with the highest postfit RMS of phase ***,the evolution of the vegetation around the antenna should be considered as it could cause a progressive loss of quality,which is not complying with the IGS *** quality assessment shows that the Topo-Iberia stations are appropriate for geodetic purposes,but permanent monitoring would be necessary to avoid the least possible loss of data and *** addition,a method to characterize the GNSS data quality is proposed.

关键词： GPS dataquality's effects IGS quality standard Postfit LC phase residual Qualityassessment Topo-Iberia CGPS network

Comparing Fine-Tuning, Zero and Few-Shot Strategies with Large Language Models in Hate Speech Detection in English

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Computer Modeling in Engineering & Sciences 2024年第9期140卷 2849-2868页

作者： Ronghao Pan JoséAntonio.garcía-Díaz Rafael Valencia-garcía Departamento de Informática y Sistemas Universidad de MurciaCampus de EspinardoMurcia30100Spain

Large Language Models(LLMs)are increasingly demonstrating their ability to understand natural language and solve complex tasks,especially through text *** of the relevant capabilities is contextual learning,which involves the ability to receive instructions in natural language or task demonstrations to generate expected outputs for test instances without the need for additional training or gradient *** recent years,the popularity of social networking has provided a medium through which some users can engage in offensive and harmful online *** this study,we investigate the ability of different LLMs,ranging from zero-shot and few-shot learning to *** experiments show that LLMs can identify sexist and hateful online texts using zero-shot and few-shot approaches through information ***,it is found that the encoder-decoder model called Zephyr achieves the best results with the fine-tuning approach,scoring 86.811%on the Explainable Detection of online Sexism(EDoS)test-set and 57.453%on the Multilingual Detection of Hate Speech Against Immigrants and Women in Twitter(HatEval)***,it is confirmed that the evaluated models perform well in hate text detection,as they beat the best result in the HatEval task *** error analysis shows that contextual learning had difficulty distinguishing between types of hate speech and figurative ***,the fine-tuned approach tends to produce many false positives.

关键词： Hate speech detection zero-shot few-shot fine-tuning natural language processing

online Demand Response Characterization Based on variability in Customer Behavior

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Journal of Modern Power Systems and Clean Energy 2024年第3期12卷 936-946页

作者： Lester Marrero Daniel Sbárbaro Luis garcía-Santander the Department of Electrical Engineering University of ConcepciónConcepción 4070409Chile

This paper proposes an online framework to characterize demand response(DR)over *** proposed framework facilitates obtaining and updating the daily consumption patterns of *** essential concept of response profile class(RPC)is introduced for characterization and complemented by the measure of the variability in customer *** paper uses a modified version of the incremental clustering by fast search and find of density peaks(CFSFDP)algorithm for daily profiles,considering the multivariate normal kernel density estimator and incremental forms of the Davies-Bouldin(i DB)and Xie-Beni(i XB)validity *** studies conducted using real-world and simulated daily profiles of residential and commercial Chilean end-users have demonstrated how the proposed framework can continuously characterize *** proposed framework is proven to achieve realistic customer models for effective energy management by estimating the customer response to price signals at the distribution system operator(DSo)level.

关键词： Demand response(DR) incremental indice online characterization online clustering response profile class(RPC)